Temperature driven evolution of thermal, electrical, and optical properties of Ti–Al–N coatings

Abstract

Monolithic single phase cubic (c) Ti1−xAlxN thin films are used in various industrial applications due to their high thermal stability, which beneficially effects lifetime and performance of cutting and milling tools, but also find increasing utilization in electronic and optical devices. The present study elucidates the temperature-driven evolution of heat conductivity, electrical resistivity and optical reflectance from room temperature up to 1400 °C and links them to structural and chemical changes in Ti1−xAlxN coatings. It is shown that various decomposition phenomena, involving recovery and spinodal decomposition (known to account for the age hardening phenomenon in c-Ti1−xAlxN), as well as the cubic to wurtzite phase transformation of spinodally formed AlN-enriched domains, effectively increase the thermal conductivity of the coatings from ∼3.8 W m−1 K−1 by a factor of three, while the electrical resistivity is reduced by one order of magnitude. A change in the coating color from metallic grey after deposition to reddish-golden after annealing to 1400 °C is related to the film structure and discussed in terms of film reflectivity.

Microstructure evolution during the isostructural decomposition of TiAlN—A combined in-situ small angle x-ray scattering and phase field study

“…7,19 However, these inhomogeneities are on an intensity scale lower than what could be resolved with the used SAXS set up or by WAXS in earlier publications. 4,5,7,9,10,17,22,39 Figure 3 shows that when the annealing temperature is reached a SAXS peak is immediately present. This suggests that the spinodal decomposition starts instantaneously at, or even before, the annealing temperature is attained.…”

“…12 These studies confirmed that AlN-and TiN-rich cubic domains evolve during annealing. In-situ annealing experiments have been performed with dynamic heating using differential scanning calorimetry (DSC) 5,6,21,22 and small angle x-ray scattering (SAXS), 23 from which the onset of the decomposition and the involved activation energies were determined. However, the details of the isostructural decomposition are not fully understood, i.e., c-TiAlN !…”

The Atomistic Structure of Metal/Ceramic Interfaces Is the Key Issue for Developing Better Properties

“…This development shows the trend that functional materials demand more and more interface research, because possibilities for applications increase. Representative examples of present research on inorganic interfaces are thermal-barrier coatings (TBC) [27][28][29][30], hard TiN-coating [31][32][33][34][35], superconductors [36], and as functional components in microelectronics [37][38][39][40][41][42], transparent conducting oxides (TCO) [43][44][45][46], photovoltaic materials [47], thermo-electrics [48][49][50][51][52], ferroelectrics [53], magnetic materials or spintronics [54,55].…”

Investigation of Cutting Temperature during Turning Inconel 718 with (Ti,Al)N PVD Coated Cemented Carbide Tools

“…The measured temperatures of PVD Ti 0.55 Al 0.45 N coated tool were higher than those of the PVD Ti 0.41 Al 0.59 N coated tool. This was associated with the thermal conductivity of Ti (1 −x ) Al x N coating being increased with the increase of Al concentration [18,19]. The Al concentration of Ti 0.41 Al 0.59 N coating was higher than that of the Ti 0.55 Al 0.45 N coating.…”

“…The Al concentration of Ti 0.41 Al 0.59 N coating was higher than that of the Ti 0.55 Al 0.45 N coating. Thus, the thermal conductivity of Ti 0.41 Al 0.59 N coating was higher than Ti 0.55 Al 0.45 N coating as referred to in [14,18,19]. Compared with the PVD Ti 0.55 Al 0.45 N coated tools, the heat generated can be dissipated quickly from the tool body into the environment and thus decrease the measured temperature for PVD Ti 0.41 Al 0.59 N coated tools.…”